Engineering materials continue to progress as technology advances. New materials are designed to surpass the requirements of the old. Rigidity, strength, weight, density, impact resistance, electrical and optical properties and many other material properties can be manipulated to suit a desired function. Over the past decade, polymer composites have emerged as new classes of high performance materials with unique material properties. These composites are created using two or more materials with individual material properties that combine to create a new structure with tailored properties.
In order to enhance the desired properties of these high performance materials, fillers such as fibers or particles may be imbedded into the matrix material. Normally, fillers are distributed in a uniform fashion throughout the matrix material. The heterogeneity of the fillers distributed throughout the matrix material provides predictable properties and mechanical responses of the materials. However, the spatial orientation and distribution of the fillers are strongly dependent on the ways in which the materials were prepared and processed. In other words, poor preparation and processing of the matrix material may lead to non-uniform distribution or undesirable orientation of the fillers. Further, since present methodologies contemplate the uniform distribution of the fillers throughout the matrix material, the finished composite cannot be locally tailored to have different properties in different locations.
Locally tailored, finished composites that have different properties in different locations are known as functionally graded materials. These functionally graded materials vary in composition and structure gradually over volume, resulting in corresponding changes in the properties of the material. As a result, functionally graded materials can be designed for specific functions and applications. By way of example, functionally graded materials have been developed for use in optical, biological, and electrical systems. Various processes have been utilized to fabricate these functionally graded materials such as impeller drying process (IDP), thermal spraying, controlled segregation, controlled blending, and others. However, these processes have proven drawbacks. For example, some of these processes can only be created in small laboratory quantities, while others have issues with high quality reproducibility.
Therefore, it is a primary object and feature of the present invention to provide a method for fabricating polymer composites incorporating fillers with multi-directional orientations.
It is a further object and feature of the present invention to provide a method for fabricating polymer composites incorporating fillers with multi-directional orientations that allows for the fillers to be orientated in a direction or concentration suitable for a particular composite requirement.
It is a still further object and feature of the present invention to provide a method for fabricating polymer composites incorporating fillers with multi-directional orientations that is simple, inexpensive and allows that the polymer composites to be produced on a larger scale than prior methods.
In accordance with the present invention, a method is provided of fabricating a composite incorporating fillers. The method includes the steps of depositing the fillers in a matrix material and exposing at least a portion of the matrix material to an electrical field such that the fillers in the at least a portion of the matrix material align in a first direction in response thereto. The at least a portion of the matrix material is then cured, thereby locking the desirable first filler orientation with the composite.
The at least a portion of the matrix material may be a first portion of matrix material and the method may include the additional step of exposing a second portion to matrix material to the electrical field such that the fillers in the second portion of the matrix material align in a second direction. Thereafter, the second portion of the matrix material is cured. Alternatively, the method may include the additional step of depositing the first portion of the matrix material in a mold prior to exposing the first portion of the matrix material to the electrical field. Thereafter, a second portion of the matrix material may be deposited in contact with the first portion of matrix material. The second portion of matrix material is exposed to an electrical field such that the fillers in the second portion of the matrix material align in a second direction in response thereto. The second portion of the matrix material is then cured. The first direction may be generally parallel to the second direction.
It is contemplated to disperse the fillers in the matrix material prior to exposing the at least a portion of the matrix material to the electrical field. The step of exposing at least a portion of the matrix material to an electrical field may include the additional steps of depositing the matrix material in a mold and positioning the mold at a desired location with respect to the electrical field. Alternatively, the step of exposing at least a portion of the matrix material to an electrical field includes the step of positioning the electrical field at a desired location with respect to the matrix material.
In accordance with a further aspect of the present invention, a method is provided of fabricating a composite incorporating fillers. The method includes the steps of depositing the fillers in a matrix material and inserting the matrix material into a mold. The mold is positioned at a desired location with respect to an electrical field such that at least a portion of the fillers in the matrix material align in a first direction in response thereto. At least a portion of the matrix material is then cured.
The at least a portion of the matrix material may be a first portion of matrix material and the method may include the additional step of exposing a second portion to matrix material to the electrical field such that the fillers in the second portion of the matrix material align in a second direction. The second portion of the matrix material is then cured. The first direction may be generally parallel to the second direction. Alternatively, the method may include the additional steps of depositing a second portion of the matrix material in contact with the first portion and exposing the second portion of the matrix material to the electrical field. At least a portion of the second portion matrix material is then cured.
The fillers may be dispersed in the matrix material prior to inserting the matrix material into the mold. In addition, it is contemplated for the electrical field to be positioned at a desired location with respect to the matrix material.
In accordance with a still further aspect of the present invention, a method is provided of fabricating a composite incorporating fillers. The method includes the steps of inserting the matrix material having fillers into a mold and positioning the mold within a stimulus field such that at least a portion of the fillers in the matrix material align in a first direction in response thereto. Thereafter, at least a portion of the matrix material is cured.
It is contemplated for the stimulus field to be an electrical field. At least a portion of the matrix material may be a first portion of matrix material and the method may include the additional step of exposing a second portion to matrix material to the stimulus field such that the fillers in the second portion of the matrix material align in a second direction. The second portion of the matrix material is then cured. Alternatively, the method may include the additional step of depositing the first portion of the matrix material in a mold prior to exposing the first portion of the matrix material to the stimulus field. A second portion of the matrix material is deposited in contact with the first portion of matrix material. The second portion of matrix material is exposed to the stimulus field such that the fillers in the second portion of the matrix material align in a second direction in response thereto. The second portion of the matrix material is then cured. The first direction may be generally parallel to the second direction.
The fillers may be dispersed in the matrix material prior to inserting the matrix material into the mold. In addition, the step of positioning the mold within a stimulus field may include the additional step of positioning the stimulus field at a desired location with respect to the matrix material.